Just the other day, I was looking at a lovely group of 1862 views of the Thames between London and Oxford by Victor Prout. This is a series of bucolic horizontal panoramas, carefully composed for nothing to jar. They derive from the traditions of painting; they were designed to be understood as though the viewer were there.

Landscape photography has moved on, and Landmark: The Fields of Photography, just opened at Somerset House, shows how far it has gone. Here’s a cunning self-portrait by Curiosity, Nasa’s Mars Rover. It’s a composite, and therefore arguably a fiction, and it’s a very, very long way away. But it is most assuredly still a landscape. Here is Dan Holdsworth’s huge, pale photograph of Mount St Helens seen from directly above. That one is a fiction of a different sort, a recreation of the topography from computer survey data. The perspective never changes across many dozens of miles, an impossible sight that we barely notice.

There are mountains in the shape of corporate graphs (Michael Najjar), an imaginary gorge by Joan Fontcuberta, maybe the greatest fictional photographer of them all. Justine Blau has made an Alpine diorama of photographs bent into shape and nailed in place, like a less pliant papier-mâché. Darren Almond’s views of the toxic nickel mining area at Norilsk in Siberia are attempts to photograph the traces of poisoned memory that the land can hold. Whatever else has happened to the landscape tradition, it has lost any residual innocence. This is arch stuff, knowing and referential.

Take a lovely view of the construction of the bridge immediately below the Hoover Dam, by Jamey Stillings. Stillings performs an odd sleight of hand, in which the temporary pylons used in construction look like time-lapse images, their successive angles more and more improbable. That great dam was one of the totems of the New Deal, and although another dam graced the first cover of Life magazine in 1936, there is a tidy significance in photography coming back to the great monuments of American documentary.

Landmark is a big show, and one of perfect museum quality. It has great photographs scattered all over it, familiar and unfamiliar. It has scholarship and verve, and is good fun to visit. It’s an overview of the past 20 or so years of a practice that the curator, William Ewing, argues is as close to the core of photography as portraiture. If there is any common theme, it is that the photographers are now (courtesy of the internet) acutely aware of each other’s work. To make a new series they have to take into account the stuff that we already know and share. The show is partly about photographers finding room to make pictures distinctly their own in a world in which everything has now been photographed. It’s less about the fight for subject matter, and more about the fight for style.

A number of photographers have been thinking very big. Edward Burtynsky’s examinations of our dependence (upon first oil and now water) add up to huge chronicles, even though they are represented in this show by only a handful of pictures. In another register, Chris McCaw’s elegant (yet frightening) Sunburned series – the negative literally burnt by the sun as it passes overhead – treats of vast, elemental issues.

Not all photographers have the mastery of those two at leading us to see the big questions. There’s a lot of aerial photography in this show (taken from kites and helicopters and spacecraft, as well as invented by computers) and that always adds up to big views. Quite a number of photographers tackle global issues even when the picture space itself is not enormous. Population, water, climate change, the constant interference of man in the landscape . . . This produces images that make big claims, but it may not be what photography does best.

Photography thrives on the particular. The detail is often the bit that sticks in the mind to snag big ideas most perfectly. Scott Conarroe shows a double arc of concrete curving out over the sea at Biloxi, Mississippi, to make room for cars to travel at speed. The particular? A little wooden walkway follows the arc exactly, for pedestrians, who don’t need it.

But digital printing and the possibility of cleaning prints up mean it is the details that are often smoothed away. A preponderance of aerial photography means you can’t see the little things anyway – just pattern. This is a very clean show: to a fault. Too many of these photographers are taking too much control in post-production for the happy accidents upon which photography thrives to have a chance. It is becoming acceptable for pictures to have all the shiny commercial gloss of advertising, with none of the targeted messaging that advertising also insists upon.

The exhibition is arranged by elegantly abstract themes, through the pleasant warren of Somerset House, and Ewing has made masterly changes of register from one to another. A section called Hallucinations is a surprise (although the landscape can always be a space of dreams). It includes a couple of pictures by John Stezaker, in which a vintage portrait, reclaimed, is overlaid with a little postcard view that blocks the face but seems to give access to the ideas within. Those are really strong.

So are a number of others where the general is arrived at through the particular. Olaf Otto Becker’s river of a most unearthly hue, running where the ice shouldn’t have melted, is fast becoming a modern colour classic. A marvellous snowscape reminiscent of Brueghel is by Peter Bialobrzeski. Ice and snow, in fact, are a theme. Two terrific studies of the high mountains by Matthieu Gafsou show plastic sheeting being laid on ice to preserve it for a bit more of the tourist season. The sheeting is white (presumably to reflect the sun as efficiently as possible) and looks for all the world like a sad parody of snow, too little, too late.

One of the most likeable pieces is a bravura time-lapse film called “Étang de Pezières II” by Jeffrey Blondes. It’s 52 hours long, and changes in the proportion of an hour of viewing representing a week of filming. The subject is a screened view of water through trees but the fascination is in the changes of light and the different rhythms of movement. It’s very close in spirit (although different in technique) to David Hockney’s nine-screen films, where movement and the perception of movement are part of the experience of seeing the landscape.

There are few conclusions to be drawn from this great scope, except that bigger claims do not necessarily add up to better pictures. Lee Friedlander’s landscapes through his car window get better every time I see them. Ewing has been courteous to British photographers: John Davies’ immaculate urban views, Harry Cory Wright’s seascapes, a number of thoughtful works by Simon Roberts and Susan Derges and Mark Power, all well represented and to advantage. So are many others. It’s an ambitious show and it doesn’t fall short. Some pictures don’t stack up, but they won’t be the same for everyone. It’s informative, a challenge and a pleasure.